Grinding mill



May 9, 1939.

' B; scHERBAuM 2,I57,462

GRINDING MILL Filed NO. 26, 1935 3 Sheets-Sheet l Www? mmm May 9, 1939- O B. scHl-:RBAUM 2,l57,462

GRINDING MILL Filed Nov. 26, 1935 :s sheets-sheet 2 May 9, 1939. B. scHERBAuM GRIDING MILL Filed Nov. 26. 1955 3 Sheets-Sheet 3 Patented May 9, 1939 GRINDING MILL Bernhard Scherbaum, Munich, Germany, assignor, by mesne assignments, to Alexanderwerk A.

Von Der Nahmer Aktiengesellschaft.

Rem-

scheid, Germany, a German company Application November 26, 1935, Serial No. 51,661 In Germany November 29, 1934 8 Claims.

This invention relates to a grinding mill comprising coaxial toothed discs, in which the grinding teeth of a stationary disc intermesh with the grinding teeth of a movable disc, the teeth and the interdental spaces of the two discs being arranged in concentric rings about the common axis of the discs. In such grinding millsyboth in the case in which the axis of the discs is horizontal and in the case in which such axis is vertical, the material is fed to the mill by a supply hopper disposed centrally of the discs. In grinding, in consequence of the centrifugal action of the rotating disc, the material or grist is impelled outwardly through the interdental spaces from ring to ring towards the periphery and is then led away through discharge openings to a storage container.

I have now ascertained as the result of experimental research that, to obtain the best results in grinding, it is important that from the time of its entrance into the mill, the material should be able to detach itself readily from the innermost teeth and to fiow in a positive predetermined path to the periphery of the discs.

The invention hasfor its object to provide a grinding mill of the type referred to, the axis of which may be either Vertical or horizontal, in which the material is guided in its passage through the mill in the manner indicated, in order to obtain the desired grinding efliciency with maximum saving of the material and of the mill.

This object is realized by the provision of a grinding mill of' the tcothed disc type, the novelty of which resides in the feature that the inner fianks of the inner teeth, by the rounding of their end faces and the provision of a tangential face, and by arrangement of the teeth in more or less radial rows tapering towards the periphery, are adapted to provide a positive fiow of the material from the point of entrance to the periphery. A i

Further features of the invention appear from the following description with reference to the accompanying drawings and will be pointed out in the claims. i

Several embodiments of the invention are illustrated in the drawings in 'wh/ich Fig. l isav Pig. 3a. shows a modification of the grinding teeth according to Fig. 3 located at the inlet of the mill insofar as these teeth are provided only with a. sharp edge while the other face is rounded.

Fig. 4 shows diagrammatically the cooperation of teeth arranged in arcuate rows with teeth arranged in straight radial rows.

Fig. 5 shows diagrammatically the cooperation of grinding discs both provided `with teeth arranged in similar arcuate rows.

Pig. '6 shows diagrammatically the Cooperation of two toothed discs having teeth arranged in arcuate rows of unequal radius.

Fig. 7 shows to a larger scale a guiding tooth constructed according to the invention.

Flg. 7a shows likewise to a larger scale a giodication of a guidingv tooth according to g.

Fig. 7b' showslikewise to a larger scale another modification of such a tooth.

Fig. 8 is a section of the tooth on the line VIII-VIII of Fig. 7.

Fig. 9 is a section of a tooth of the smallest ring of teeth represented in Fig. 3.

Fig. 10 shows a partial clevation of the means for mounting the stationary and the rotary disc. According to Flg. 1 the grinding disc a has on its grinding face b grinding teeth c of circumferential dimensions dimnishing from the centre of the4 disc towards the periphery and having their end orworking edges parallel to radii of the disc. In the peripheral zone the outermost rings of teeth have the equal number of grinding teeth. A small proportion of the number of grinding teeth are arranged in the `lform of three long spiral rows spaced apart. Between these long .rows are arranged spiral rows r, said rows starting at selected distances from the inlet d, all said rows of teeth r and interdental spaces s being arranged in similar arcs. The grinding teeth and the interdental spaces of one ring of teeth are of the same or of substantially the same width in the peripheral.

zone. By this arrangement of the grinding teeth shown in Fig. 1 the grinding face represents an inner portion of relatively few teeth and with interdental spaces of great width and a peripheral portion of a great number of smaller teeth with interdental spaces of smaller width. Thus, all the material or grist flowing through the mill is subjected to the action of centrifugal force, without being banked up in front of the peripheral zone, so that it flows gradually into the peripheral zone. The arrangement of the teeth in arcuate rows on the rotary disc has the effect that also in the inner portion of the grinding face, with counter-clockwise movement there occurs a checking action, and with clockwise movement acceleration of the fiow of the grist occurs.

- lated in relation to one another that in a single grinding operation there can be eifected grinding to equal granular sizes without any blockage. The innermost teeth cl located at the inlet d of the mill have another form than the vother teeth c. The teeth c1 are formed to guide the material quickly and without hindrance in front of the working edges of the teeth c. In Figs. 7, '7a and '7b three modifications of these teeth cl are represented to a larger scal'e, the function of which is described in detail later on. i

Fig. 2 shows in a fragmentary view the stationary disc a. to mate with the disc of Fig. 1.

The grinding teeth z' are arranged in radial rows, four rows extending to the inlet d. The innermost ring of teeth is the second smallest of the entire mill, the teeth of said ring engaging with their inner fianks l the outer flanks nl of the innermost teeth of the rotary disc (see Fig. 1) The number of teeth at the inlet is not restricted to four. The inner fiank l of each of these stationary teeth extends concavely in a circular are. Indeed these tooth flanks are near the inlet but with their end edges` formed as working faces the teeth exercise no influence on the infiow of the grist. 'I'he radial rows of teeth and the rows of interdental spaces in the peripheral zone are of equal breadth or of about equal breadth.

The half disc shown in Fig. 3 is represented as a rotary disc in which again the tooth flanks located at the inlet d` are formed as guiding faces according to the invention.' These teeth are provided with end faces l. An arcuate arrow :c indicates the direction of rotation. The arrows y extending from the guiding face to the left and upwardly indicate the direction of guidance of the grist and show how the latter is led in front of the next working edges of the end faces.

Fig. 3a shows a modification of the grinding teeth c'l'according to Fig. 3 in which the tooth C5 is provided only with one sharp edge ll while the other end face of the tooth is rounded.

Fig. 'i shows diagrammatically in What way the main rows e of the teethc of the rotary disc (Fig. 1) intersect with the main rows el of the teeth z' of the stationary disc (Fig. 2) on rotation.

The full arcuate lines e denote rows of teeth of the rotary disc according to Fig. 1 while the chain lines denote rows' of teeth of the stationary disc according to Fig. 2. It is thus to be seen that with counter-clockwise rotation in the direction of the arrows the arcuate rows of teeth and the rows of teeth of the stationary disc according to Fig. 2 cut in shearing fashion from the outside inwardly. The flow of the grist is thus restricted and increased fineness of grinding' is effected. With clockwise rotation the rows of teeth of the stationary disc cut from the centre outwards, which effects acceleration of the fiow of the grist and results in a larger granular size. In itself, however, the shearing action involves a great economy of power with uniform power requirements, because the rows of teeth do not cut or shear over their entire length but only at their points of out.

Fig. 5 shows the intersection of rows of teeth located on arcs of equal curvature on both grinding faces the progress of cut being from the outside inwardly. The arcuate rows 'of teeth of the rotary disc are indicated in full lines: those of the stationary disc are indicated by chain lines.

According to Fig. 6 the arcuate rows e of teeth of the rotary disc have a greater curvature, so that cutting from the outside inwardly is effected at a small cutting angle.

The number of rows e of teeth extending from the inlet to the periphery is not restricted to that shown in Figs. 1 and 3 but may be greater or less: Also the number of shorter rows of teeth maybe greater or less. The rows s of interdental e spaces of equal breadth in the peripheral zone are made broader roundthe grinding face for .more plentiful flow of material, but for restricted fiow they are formed of less width than the length of the teeth r and cl.

Fig. '7 shows'to a larger scale a grinding tooth cl according to Fig. 1. Theytooth fiank of this toothis at an obtuse angle to the base of the tooth and presents a face tangential to a* circle concentric with the grinding disc. The ends of said fiank and the adjoining ends of the tooth are rounded and intersect the outer flank nl at the edges h. The tooth flank need not present a tangential face but may be, for example, at an angle to the radius as indicated at 7' in Fig. 7a. Instead of having a tangential face as specified,

. the inner tooth fiank may present a concave face as indicated at m in Fig. 7b.

In Figs. 7a and 7b modified grinding teeth c2 and 03 are shown.

By the rounding of the end faces of the inner fianks of the teeth in the smallest ring of teeth and by the formation of the inner portion of the inner flank of each of said teeth with a suitable guiding face which may be either a plane tangential face or may be a concave face, and by arranging suitably in relation to one another teeth diminishing in size towards the periphery in rows, the material fed to the centre detaches itself positively from the grinding teeth of the smallest ring of teeth and is conveyed positively into the interdental spaces and thence to the periphery of the discs.

The tooth crown lc is roundedjas shown in Fig. 7. The section of the tooth on the line VIII-VIII is shown in Fig. 8. The section according to Fig. 8 shows a tooth flank rising at an obtuse angle to the face of the tooth. In the figure this angle is indicated by a, and is greater than 90.

Fig. 9 is a section through a tooth of the smallest ring of teeth of Fig. 3, and shows a tooth flank 2 extending in an are differentiaily of the tooth crown according to Figs. 7 and 8. i

Also in the rotary discs the` selection of the number of grinding teeth does not form part of the invention, so that unlike what is shown in Fig. 1, the inlet may be bounded by fewer than or by more than three teeth.

In Figure 10 the mounting'of the rotary disc and the stationary disc are shown. The rotary disc a is fixed to a shaft III, which is driven from any desired source of power. The shaft IO may be mounted in any suitable bearings. The stationary disc such as that shown in Figure 2. is

fixed to the stationary abutment by any desired means.

Iclaimz- I 1. In a grinding mill the combination with a .stationary disc and a movable disc coaxial with said stationary disc, said`discs provided with intermeshing teeth projecting from the adjacent faces of the discs, said teeth being arranged in rings concentric with said discs and being curved along said concentric rings, the circumferential dimensions of the teeth diminishing in the'direction from the center towards the periphery of said discs and the number of teeth in certain of being arranged in rows directed from the center of the discs towards the periphery with lanes of interdental spaces between said rows, adapted to guide the material to be ground positively from the center to the periphery of the disc.

2. In a grinding mill the combination with a stationary disc and a movable disc coaxial with said stationary disc, said discs provided with 'intermeshing teeth projecting from the adjacent .faces of the discs, said teeth' being arranged in ,rings increasing in the direction from the center towards the periphery, the inner flanks of the teeth of the innermost row' of said movable disc being composed of a face tangent'ially to a circle about the center of said rotatable disc, and of end faces being rounded, all of said teeth being arranged in rows directed from the center of the discs towards the periphery with lanesv of .interdental spaces between said rows, adapted to guide the material to be ground positivelyA from the center to the periphery of the disc,'each discbeing provided with small grinding teeth in the peripheral zone and with large teeth in the middle part of the disc, said small teethbeing arranged to form with the interdental spaces similarly directed rows'of equal width and being arranged to surround the middle part of the disc -in a', ringshaped manner, said large teeth being equally distributedl over the disc and those large teeth as well as their corresponding interdental spaces being arranged to form similarly directed rows formingthe continuation of the rows of Vthe peripheral zone.

3. In a grinding mill the combination with a stationary disc and a movable disc coa'xial with saidstationary disc, said discs provided with intermeshing teeth projecting from the adjacent faces of the discs, fsaid teeth being arranged in said discs and the number of teeth in certain of the rings increasing in the direction from the center'towards the periphery, the inner fianks of the `teeth of the innermost row of said movable and of end faces being rounded, all of said teeth being arranged in rows directed from the center of the discs towards the periphery, said rows of teeth starting from points unequally spaced from the center of the discs and having lanes of interdental spaces between them, adapted to guide the ma- 'terial to be ground positively from the center to the periphery of the disc.

4. In, a grinding mill the combination with a stationary disc and a movable disccoaxial with said stationary disc, said discs provided with intermeshing teeth projecting from the adjacent faces of the discs, said teeth being arranged in' ringsconcentric with said discs and being curved alongl said concentric rings, the circumferential dimensions of the teeth diminishing in the direction from the center towards the periphery of said discs and the number of teeth in certain of the rings increasing in the direction from the center towards the periphery, the inner flanks of the teeth of the innermost row of said movable disc being composed of a face tangentially to a circle about the center. of said rotatable disc, and of end faces, said 'rotary disc being provided with spiral rows of teeth from the periphery towards the center and said stationary disc being provided with straight radial rows of teeth, all of said teeth being arranged in rows directed from the center of the discs towards the periphery with lanes of interdental spaces between said rows, adapted to guide the material to be' ground positively from the center to the periphery of the disc.

5. In a grinding mill the combination with a stationary disc and a movable disc coaxial with said stationary disc, said discs provided with intermeshing teeth projecting from the adjacent faces of the discs, said teeth being arranged in rings concentric with said discs and being curved along said concentric rings, the circumferential dimensions of the teeth diminishing in the direction from the center towards the periphery of said discs andthe number of teeth in certain of the rings 'increasing in the direction from the center towards the periphery, the inner fianks of the teeth of the innermost row of said mov- -able disc being composed of a face tangentially to a circle about the center of said rotatable disc,

and of end faces being rounded, all of said teeth of said rotary and stationary disc being arranged in arcs of teeth of equal curvature and directed from the center of the discs towards the periphsaid stationary disc, said discs provided with intermeshing teethprojecting from the adjacent faces of the discs, said teeth being arranged in rings concentric with said discs and being curved along said concentric rings, the circumferential dimensions of the teeth'diminishing in the direction from-the center towards the periphery of said discs and' the number of 'teeth in certain of the rings increasing in the direction from the center towards' the periphery, the inner' flanks of the teeth of the innermost row of said movable disc being composed of a face tangentially.

to a circle about the' centerof said rotatable disc, and of end faces being rounded, said teeth of said rotary and stationary disc being arranged in arcs of teeth of different curvature and directed from the center of the discs towards the periphery with lanes o f interdental spaces between said rows, adapted to guide the material to be ground positively from the center to the periphery of the disc.

7. In a grinding mill the combination with"a stationary disc and a movable disc coaxial with said stationary disc, said discs provided with intermeshing teeth projecting from the adjacent faces of the discs, said teeth being arranged in rings concentric with said discs and being curved along said concentric rings, the circumferential dimensions of the teeth diminishing in the direction from the center towards the periphery of said discs and the number of teeth in certain of the rings increasing in the direction from the center towards the peripheryythe inner fianks of the teeth of the innermost row of said movable disc composed of a face tangentially to a circle about the center of said rotatable disc, and of end faces, both of which being rounded in peripheral vdirection towards the outer tooth fiank and intersectng the latter along sharp knife edges, all of said teeth being arranged in rows directed from the center of the discs towards the periphery with lanes of interdental spaces between said rows, adapted to guide 'the material to be ground positively from the center to the p`eriphery of the disc.

' to the periphery of the disc.

8. In a grinding mill the combination with a stationary disc anda movable disc coaxial with said stationary disc, said discs provided with intermeshing teeth projecting froni the adjacent faces of the discs, said teeth being arranged in rings concentric with said discs and being curved along said concentric rings, the circumferential dimensions of the teeth .diminishing in the direction from the center towards the periphery of said discs and the number of teeth in certain of the rings increasing in the direction from the center towards the periphery, the inn'er fianks of the teeth of the innermost row on said movable disc being composed of a face tangentially 'to a circle about the center of said rotatable disc,

and of en'd faces on said tangentially arranged teeth, only one of which on each tooth being of wedge shape, all of said teeth being arranged in rows directed from the center of the discs towards the periphery with lanes of interdental spaces between said rows, adapted to guide the material to be ground positi'vely from the center BERNHARD SCHERBAUM. 

